In Vitro Low-Bortezomib Doses Induce Apoptosis and Independently Decrease the Activities of Glutathione S-Transferase and Glutathione Peroxidase in Multiple Myeloma, Taking into Account the IGSTT1/I and IGSTM1/I Gene Variants

Background: Multiple myeloma (MM) is a malignancy derived from plasma cells. Bortezomib affects the concentration of reduced glutathione (GSH) and the activity of glutathione enzymes. The aim of our study was to analyze deletion (null/present) variants of GSTT1 and GSTM1 genes and their association with the levels of glutathione and its enzymes in bortezomib-treated cell cultures derived from MM patients. Materials and Methods: This study included 180 individuals (80 MM patients and 100 healthy blood donors) who were genotyped via multiplex PCR (for the GSTT1/GSTM1 genes). Under in vitro conditions, MM bone marrow cells were treated with bortezomib (1–4 nM) to determine apoptosis (via fluorescence microscopy), GSH concentration, and activity of glutathione enzymes (via ELISA). Results: Bortezomib increased the number of apoptotic cells and decreased the activity of S-glutathione transferase (GST) and glutathione peroxidase (GPx). We found significant differences in GST activity between 1 nM (GSTT1-null vs. GSTT1-present), 2 nM (GSTT1-null vs. GSTT1-present), and 4 nM (GSTM1-null vs. GSTM1-present) bortezomib: 0.07 vs. 0.12, p = 0.02; 0.06 vs. 0.10, p = 0.02; and 0.03 vs. 0.08, p = 0.01, respectively. Conclusions: Bortezomib affects the activities of GST and GPx. GST activity was associated with GSTT1 and GSTM1 variants but only at some bortezomib doses.